This study proposes to investigate the treatment response of body dysmorphic disorder (BDD) in adolescents. Body dysmorphic disorder, a preoccupation with an imagined or slight defect in appearance, is a distressing and impairing disorder that is more common than is generally recognized. BDD usually begins during childhood or adolescence, but its treatment in adolescents has not been investigated. Such investigation is important because BDD appears to often be chronic and to cause considerable morbidity. It is associated with high rates of social and academic/occupational impairment, being housebound, psychiatric hospitalization, suicidal ideation, and suicide attempts. Preliminary data from adults and adolescents suggest that BDD and its delusional variant (a type of delusional disorder, somatic type) may respond to serotonin-reuptake inhibitors. Furthermore, similarities between BDD and obsessive compulsive disorder (OCD) make these medications promising for adolescent BDD. The primary specific aim of this study is to assess the efficacy and safety of fluoxetine vs placebo in BDD and its delusional disorder variant in 100 adolescents age 13-17. The proposed study will be a 12-week double-blind parallel-groups trial that will occur at three sites: Butler Hospital/Brown University, Mount Sinai School of Medicine, and The University of Cincinnati School of Medicine. A secondary specific aim is to explore predictors of treatment response. The hypothesis to be tested is that delusionality (insight), comorbid major depression or OCD, and illness severity will not predict fluoxetine response. The proposed study will provide needed data on BDD's treatment in adolescents. It will be the first controlled treatment trial of BDD in an adolescent age group. Such investigation is needed because this under recognized often-secret disorder usually begins during adolescence and can cause significant distress and impairment in functioning. When untreated, adolescent-onset BDD appears to often interfere with the developmental tasks of adolescence, to persist, and to cause substantial morbidity throughout the life span.